Method for plastic deformation of polymers by electromagnetic radiation

ABSTRACT

According to the invention, a method for the plastic deformation of a polymer is provided, which is characterized in that the polymer is treated with electromagnetic radiation having a wavelength in the range from 0.8 to 100 μm with simultaneous action of pressure and shearing and thermal energy. By means of the method according to the invention, it is also possible to plastically deform polymers which have to date not been accessible to plastic deformation, such as chitin and in particular cellulose.

The invention relates to a method for the plastic deformation ofpolymers, in particular of polymers which can be plastically deformedonly with difficulty or not at all by conventional methods, such aspolymers which form intermolecular hydrogen bridge bonds and inparticular cellulose, chitin and polyvinyl alcohol. The invention alsorelates to an apparatus for carrying out the method, and plasticallydeformed cellulose and plastically deformed chitin which are obtainableby the method according to the invention.

Methods for the plastic deformation, in particular for the thermoplasticdeformation, of polymers have long been known and are used to aconsiderable extent in industry. In addition to injection mouldingmethods, they also include in particular extrusion methods and methodsfor the production of man-made fibres from spinning mills. In thesemethods, polymers are melted using thermal energy. Infrared lamps andhigh frequency lamps (for example WO 96/22867) or microwaves (forexample WO 98/14314) are also used as thermal energy sources, inaddition to customary heating apparatuses. In these known methods forthe melting of polymers, in which electromagnetic radiation is used,electromagnetic radiation is used unspecifically, i.e. in order tosupply heat energy to the polymer system, and accordingly notmonochromatic radiation but radiation in a broad wavelength range isused.

While the known methods can be used without problems in the case of mostpolymers, the thermoplastic processing and the melting of polymers whichform strong intermolecular interactions, as occur in particular in thecase of hydrogen bridge bonds, is possible only with great difficultiesor is not possible at all.

Thus, it is known that cellulose does not melt but undergoes degradationabove 180° C. under the action of oxygen (e.g. Ullmann's encyclopedia ofindustrial chemistry, 5th edition, Volume A5, 1986, 383). The reason forthis is that the polymer chains of the cellulose are held by thesecondary valency hydrogen bridge bonds in a fixed crystal lattice whichhas to be destroyed for the thermoplastic processing or the melting. Attemperatures which would be required for thermal breaking of thesecondary valency bonds, however, the polymer chain is irreversiblydamaged. The thermal load capacity of the molecular chains of celluloseis accordingly not greater than the thermal stability of the celluloselattice structure fixed by the secondary valencies from hydrogen bridgebonds (e.g. Das Papier [Paper], 44 (1990) 12, 617-624; TAPPI Journal 67(1984) 12, 82/83; Journal of Applied Polymer Science, 37 (1989),3305-3314). There is therefore a lack of a temperature interval,required for thermoplastic processing, between the temperature at whichthe intermolecular bonds break and the temperature at which themolecular chains are thermally damaged.

Although it is possible to process cellulose from a solution, forexample to give films and fibres, such methods have a number ofdisadvantages. Thus, the rate for methods for polymer formation from apolymer solution is controlled by mass transfer (e.g. coagulation), andsuch methods are far inferior to the thermoplastic processes withrespect to their rate. For example, cellulose fibres can be producedonly at a rate of up to about 100 m/min, while thermoplastic materialcan be processed to fibres at rates of up to 8000 m/min. The result ofthis is a considerable cost disadvantage of the cellulose fibres.Furthermore, unusual and hazardous substances which give rise to highprocess costs have to be used as solvents for cellulose. Thus, thesolvent carbon disulphide (CS₂) was initially used for cellulose but isreadily flammable and explosive in vapour form and moreover has toxicproperties. The N-methylmorpholine N-oxide (NMMO) which has beencustomary recently is also not without problems since it forms explosiveperoxides at elevated temperatures (Kaplan, D. L.: Biopolymers fromRenewable Resources, Berlin, Springer 1998, 79).

In the case of chitin, another natural polysaccharide, the processingsituation is similarly difficult since it too tends to undergo thermaldecomposition (at about 280° C.) rather than to melt (Kaplan, D. L.:Biopolymers from Renewable Resources, Berlin, Springer 1998, 108).

In the case of both natural products, attempts were made to solve theproblem of the lack of thermoplastic processibility by a chemicalmodification. Thus, cellulose is esterified, for example, to cellulosenitrate, acetate, propionate or butyrate, which weakens the hydrogenbridges as intermolecular bonds. The method is effective but complicatedand expensive. Moreover, one of the most important properties of thecellulose is its good biodegradability and, while the thermoplasticprocessibility of the cellulose is improved with increasing degree ofsubstitution, the biodegradability decreases with increasing degree ofsubstitution (Journal of Applied Polymer Science, 50 (1993), 1739-1746).Accordingly, chitin is frequently deacetylated to chitosan prior toindustrial use. In addition to the disadvantages described above, theindustrial deacetylation is moreover economically and ecologicallyproblematic owing to the required amounts of alkali.

These difficulties which arise in the case of thermoplastic processingof cellulose and of chitin are particularly serious since both celluloseand chitin are synthesized in large amounts in nature and are the mostimportant renewable polymers. According to literature data, cellulose ismost frequent and chitin the second most frequent raw material on Earth(Kaplan, D. L.: Biopolymers from Renewable. Resources, Berlin, Springer1998, 96).

In the case of other polymers which have intermolecular hydrogen bridgebonds, thermoplastic processing is on the other hand possible since themolecular chains are sufficiently thermally stable so that melting orthermoplastic deformation can take place at temperatures at which thesecondary valency hydrogen bridge bonds break. A typical example of thisis polyamide 6, in which the crystalline arrangement of the molecularchains melts at 230° C. owing to breaking of the hydrogen bridge bonds(Domininghaus, H.: Die Kunststoffe und ihre Eigenschaften [The plasticsand their properties], 5th edition,. Springer, Berlin 1998, 616). Sincethe molecular chains of polyamide 6 may be exposed to temperatures up to300° C. before they are thermally damaged, it is possible to melt orthermally deform polyamide 6. In practice, typical processingtemperatures are 230° C. to 280° C.

Although thermoplastic processing is possible and is carried out on alarge scale in the case of such polymers, the high temperatures whichare required for this purpose are not advantageous. There is a need fora method by means of which these basically thermoplastically processiblepolymers can also be melted and subjected to plastic processing with theuse of less energy.

The difficulties described in the case of the thermoplastic processingalso occur, for example, in the case of polyvinyl alcohol.

It is therefore an object of the invention to provide a novel method forthe plastic deformation of a polymer, by means of which it is alsopossible in particular to process those polymers which, owing to strongintermolecular interactions, especially owing to hydrogen bridge bonds,can be melted or plastically deformed only with difficulty or not at allby conventional methods.

It is furthermore an object of the invention to provide an apparatus forcarrying out such a method.

Finally, it is an object of the invention to provide the polymerscellulose and chitin, which have not been thermoplastically deformableto date, in a novel modification as formed on plastic deformation by themethod according to the invention.

These objects are achieved by a method for the plastic deformation ofpolymers, which is characterized in that a polymer is treated withelectromagnetic radiation having a wavelength in the range from 0.8 to100 μm with simultaneous action of pressure and shearing and thermalenergy. An apparatus for carrying out this method is also provided,which comprises means for holding a polymer, means for exerting pressureon the polymer, means for shearing the polymer and means for supplyingor removing heat and means for irradiating the polymer withelectromagnetic radiation having a wavelength in the range from 0.8 to100 μm.

Finally, the method also provides a polymer which contains cellulose orchitin and which can be prepared by the method according to theinvention.

In the context of the present invention, stated percentages are based onpercent by weight and molecular weights of polymers are based on numberaverage molecular weights, unless stated otherwise.

In contrast to the methods of the prior art, as described, for example,in WO 96/22867 and Wo 98/14314, which use electromagnetic radiation andalso infrared lamps (WO 96/22867) as heat sources and thus do not useelectromagnetic radiation of a specifically defined wavelength but as arule broadband electromagnetic radiation (this is most suitable fortransmitting heat to a system), in the method according to the inventionthe polymer to be processed is selectively treated with electromagneticradiation of a defined wavelength, i.e. substantially monochromaticradiation, the wavelength being selected from a range from 0.8 μm to 100μm.

The following statements relating to processes in the polymer to bedeformed explain the invention, but the invention is not limited to theassumed mechanisms.

The method according to the invention is based on the principle that thesecondary valency bonds in polymers, in particular hydrogen bridgebonds, are specifically broken by a nonthermal method. For this purpose,the polymer is exposed to three different types of energy, namely energyfrom electromagnetic radiation of a suitable wavelength, mechanicalenergy and thermal energy. It is currently assumed that, in the methodaccording to the invention, the hydrogen bridge bonds are weakened bymechanical and thermal energy. The energy introduced into the system viathe electromagnetic radiation then results in the hydrogen bridge bondsbeing broken. As a result of the shearing acting on the polymer, thepolymer is then plastically deformed. If the energy input is stopped andthe plastic deformation ceases, the molecules form new hydrogen bridgebonds.

By means of the method according to the invention, it is possible toachieve thermoplastic deformation of polymers which have secondaryvalency bonds, in particular hydrogen bridge bonds, at temperatureswhich are substantially below the temperatures which are usuallyrequired for breaking secondary valency bonds, in particular theintermolecular hydrogen bridge bonds. Thus, by means of the methodaccording to the invention, it is possible for the first time also toplastically deform polymers in which the intramolecular covalent bondenergies are of the same order of magnitude (or even below this) as theenergies of the intermolecular hydrogen bridge bonds, in particularcellulose and chitin. In particular, it is possible for the first timeby means of the method according to the invention to plastically deformcellulose and to convert it into a transparent, clear film.

The invention makes use of the fact that secondary valency bonds, inparticular hydrogen bridge bonds, absorb electromagnetic radiationhaving an energy in the infrared range. At these wavelengths,destruction of the covalent polymer bonds by the electromagneticradiation is not to be feared. The electromagnetic radiation suppliedshould therefore have a wavelength of more than 800 nm, i.e. 0.8 μm.Firstly, high-energy radiation cannot be readily absorbed by thesecondary valency bonds, in particular the hydrogen bridge bonds, and,secondly, the risk that the polymer will be chemically modified isincreased by the use of high-energy radiation. On the other hand,according to the invention, the secondary valency bonds, in particularthe hydrogen bridge bonds, are weakened by supplying mechanical energyand heat energy, so that, under certain circumstances, evenelectromagnetic radiation having a very low energy is sufficient toenable the method according to the invention to be carried outsuccessfully. If, however, the wavelength of the electromagneticradiation supply is longer than 100 μm, it is as a rule too low-energyfor breaking the secondary valency bonds, in particular hydrogen bridgebonds. In the method according to the invention, electromagneticradiation having a wavelength in the range from 0.8 μm to 100 μm istherefore used. The specifically chosen wavelength depends on thepolymer to be processed and on the other reaction conditions, inparticular on the energy introduced into the system by means of theshearing and on the possibly additionally supplied thermal energy.

The wavelength most suitable for the method according to the inventioncan be determined for any polymer and any experimental arrangement by afew routine experiments. For example, the wavelength range in which thesecondary valency bonds of the polymer to be processed absorb can bedetermined by spectroscopic methods. Starting from the values thusdetermined, the wavelength which is optimum for carrying out the methodaccording to the invention is then determined by suitable routineexperiments.

Alternatively, quantum energies (photon energies) which would have tohave electromagnetic radiation in order to break the secondary valencybonds can also be calculated from the bond energies of the hydrogenbridge bonds. From these calculations, the person skilled in the artobtains a starting value for the suitable wavelength of theelectromagnetic radiation to be used in the method according to theinvention, on the basis of which value and with simple routineexperiments the wavelength most suitable for the plastic deformation ofthe chosen polymer can be determined.

As a rule, the radiation quanta may have a somewhat lower energy or thewavelength of the electromagnetic radiation used may be slightly longerthan the result of the spectroscopic measurements and theoreticalcalculations described above since, in the method according to theinvention, the secondary valency bonds are additionally weakened bymechanical and thermal load. Since, on increasing the bond distance r,the bond energies vary as 1/r^(n) (where n>1), even small extensions ofthe bond distances result in substantially lower bond energies. Thiscorresponds to longer-wave and hence lower-energy radiation.

According to the invention, the polymer is thus treated withelectromagnetic radiation of a defined wavelength which preferablycorresponds to the bond energy of the secondary valency bonds of thepolymer (in particular the hydrogen bridge bonds).

Electromagnetic radiation having a wavelength in the range from 1 μm to50 μm is particularly preferably used according to the invention.Particularly preferred is electromagnetic radiation having a wavelengthin the range from 1 μm to 20 μm and in particular of about 10 μm.Further preferred ranges of the suitable wavelength are from 0.8 μm to50 μm, from 0.8 μm to 20 μm, from 0.8 μm to 15 μm and from 1 μm to 15μm.

For practical reasons, it is expedient to use a laser for generating theelectromagnetic radiation, which is preferred according to theinvention. A carbon dioxide laser which provides radiation having awavelength of 10.6 μm is particularly preferred.

The required quantity of energy (intensity of the electromagneticradiation) depends to a very great extent on the specific apparatus inwhich the plastic deformation of the polymer is to be carried out and onthe polymer throughput. Frequently, a beam intensity of only 10² W/cm²or less is sufficient. However, it may be necessary or advantageous touse a higher beam intensity. The beam intensity is, however, preferablynot higher than 10⁵ W/cm². Particularly preferred is a beam intensity of5×10² W/cm² to 10⁴ W/cm² and especially of 10 ³ W/cm² to 10⁴ W/cm², e.g.about 10³ W/cm².

With the use of a laser, the beam may be pulsed or continuous, the beampreferably being pulsed.

The irradiation should be effected in a manner such that sufficientabsorption of the radiation in the polymer takes place. The absorptionis preferably in the range from 1 kJ/mol to 10,000 kJ/mol, morepreferably from 5 kJ/mol to 1000 kJ/mol, in particular from 5 to 30kJ/mol, e.g. about 20 kJ/mol.

The mechanical energy is introduced into the system in a manner knownper se. Through shearing, the polymer is subjected to a mechanical shearstress by means of which the secondary valency bonds are additionallysubjected to stress and are weakened. As soon as a sufficient number ofsecondary valency bonds break, the material is plastically deformed bythe shear stress. The plastic deformation is thus a shear deformation.When the plastic deformation ceases, the molecules form new secondaryvalency bonds, e.g. hydrogen bridge bonds.

The shearing is preferably applied with a force or a torque whichresults in a shear rate in the range from 10⁰ s⁻¹ to 10⁶ s⁻¹, preferablyfrom 10¹ to 10⁵ s⁻¹, in particular from 10¹ s⁻¹ to 10³ s⁻¹, for exampleabout 10² s^(−1.)

In addition to the shearing, the polymer is also subjected to a pressurewhich reduces the danger of fracturing of the material during processingand maintains a cohesive moulding material.

A pressure of 1 N/mm² to 5000 N/mm², preferably of 10 N/mm² to 1000N/mm² and in particular of 50 to 500 N/mm² is preferably exerted on thepolymer.

Pressure and shearing in cooperation introduce mechanical energy intothe polymer system. The pressure is preferably also used fortransmitting the shearing via the frictional effect into the polymer.According to the invention, this is preferably effected by means of twoparallel ram surfaces between which the polymer is present and via whichpressure is exerted on the polymer. A movement of the ram surfacesrelative to one another under pressure generally results in transmissionof shearing to the polymer.

Even in known apparatuses for the plastic deformation of polymers, suchas, for example, extruders, pressure and shearing are exertedsimultaneously on the polymer to be processed. According to theinvention, any known apparatus which is suitable for the thermoplasticdeformation or melting of polymer and by means of which pressure andshearing are transmitted to a polymer can be used after correspondingadaptation for carrying out the method according to the invention.

In the method according to the invention, it is furthermore importantfor thermal energy to act on the polymer. While thermal energy alone isnot capable of breaking the secondary valency bonds (for example thehydrogen bridge bonds) of polymers, it, like mechanical energy, weakensthe secondary valency bonds. A system on which pressure and shearing isexerted is simultaneously necessarily also supplied with thermal energy.In the method according to the invention, further thermal energy issupplied to the polymer additionally by the electromagnetic radiation.It is therefore frequently not necessary to supply thermal energyspecially to the system. If this is required, it can be effected, forexample, via a preheated material or by heating the moulds. Othermethods for this purpose are known to the person skilled in the art.

Since the method according to the invention serves in particular alsofor plastically deforming polymers which must not be subjected to hightemperatures, it may be necessary to remove thermal energy during themethod if the thermal energy introduced into the polymer by shearing andradiation leads to a temperature increase such that the polymer to beprocessed is no longer stable. In this case, cooling should be effectedduring the method. In a preferred embodiment of the method according tothe invention, the polymer to be processed is cooled during theprocessing by removal of heat.

According to the invention, the method is therefore preferably carriedout in a manner such that the temperature of the polymer is monitoredand is kept in a predetermined range by supplying or removing heat. Thetemperature which is suitable depends to a very great extent on thethermal stability of the polymer to be processed and on economicconsiderations. According to the invention, the temperature during theplastic deformation of the polymer is preferably from 20 to 280° C., thehigher temperature range not being suitable for sensitive polymers butbeing suitable for use, for example, in the processing of polyamide 6. Arange from 20° C. to 250° C. is more preferred, and thermally sensitivepolymers, such as cellulose, are preferably processed at a temperaturein the range from 20° C. to 120° C., more preferably from 50° C. to 100°C.

According to the invention, the method is preferably carried out at atemperature of T≦Tm/z−20° C., more preferably at a temperature ofT≦Tm/z−40° C., more preferably at a temperature of T≦Tm/z−60° C., whereTm/z is the temperature at which the polymer melts or, if the polymer isdecomposed before it melts, is the temperature at which the polymerdecomposes. This temperature is, for example, 180° C. in the case ofcellulose (this is a decomposition temperature), and 230° C. in the caseof polyamide (the melting point).

The polymers which can be plastically deformed by the method accordingto the invention are not particularly limited. Although the methodaccording to the invention is particularly advantageously suitable forthe processing of thermally sensitive polymers which form strongintermolecular interactions (i.e. secondary valency bonds), inparticular hydrogen bridge bonds, it is also possible to processpolymers which are thermally stable, such as polyamide 6, or polymerswhich form weaker intermolecular interactions, by the method accordingto the invention, and it is entirely possible that there will beadvantages in terms of process engineering, such as a lower processingtemperature, compared with the conventional methods.

The term polymer as used in the context of the present Applicationincludes individual polymers and blends of a plurality of polymers, inparticular blends which contain one or more polymers which have strongsecondary valency bonds, in particular hydrogen bridge bonds. Additiveswhich influence the processing properties or application properties ofthe polymer may be added to the polymers. Such additives are known tothe person skilled in the art, and, for example, glycerol, sorbitol ordyes may be mentioned here. The term polymer means both homopolymers andcopolymers. Neither the average molecular weight of the polymer nor themolecular weight distribution is subject to particular restrictions. Asa rule, the polymers have 20 or more monomer units, preferably 60 ormore monomer units, in particular 80 or more monomers units, per polymermolecule. Particularly preferably, the polymers have about 300 to 44,000monomer units per polymer molecule, particularly if the polymer iscellulose. According to the invention, the polymer to be processedparticularly preferably comprises at least one polymer which can formintermolecular hydrogen bridge bonds, in particular a polysaccharide ora polyvinyl alcohol. Polymers which comprise at least one polymer whichis cellulose, chitin, polyvinyl alcohol, a constitutional isomer ofcellulose or a constitutional isomer of chitin, particularly preferablycellulose or chitin, are particularly preferably processed by the methodaccording to the invention. According to the invention, the polymerparticularly preferably comprises 10% or more, more preferably 30% ormore, more preferably 60% or more, more preferably 75% or more, mostpreferably 90% or more, of cellulose or chitin.

According to the invention, the polymer also preferably comprises 70% ormore, more preferably 80% or more, most preferably 90% or more, of amixture of cellulose and hemicellulose, the proportion of hemicellulosepreferably being 20% or less, more preferably 15% or less, mostpreferably 10% or less. It is also possible to use pulp whichpredominantly comprises cellulose (e.g. Römpp Chemie-Lexikon [RömppChemistry Lexicon], 9th Edition, Volume 6, 1992, 5113).

Cellulose and chitin are natural products which may frequently alsocomprise low molecular weight impurities without adversely affecting thecarrying out of the method, but preferably not more than 50%, morepreferably not more than 20%, most preferably not more than 10%.Customary natural impurities of cellulose are, for example, lignin and,in isolated cases, naturally occurring substances, such as, for example,silicic acids. According to the invention, substantially pure(preferably pure) cellulose, e.g. pulp, substantially pure (preferablypure) chitin, optionally together with suitable additives as mentionedabove, are also preferably used as the polymer.

A particular advantage of the method according to the invention is thatit can be combined with methods known per se for the thermoplasticdeformation or melting of polymers, such as in particular extrusionmethods, methods for the spinning of fibres and injection mouldingmethods. In extrusion methods, pressure and shearing are exerted on thepolymer by the extruder itself. Extruders are usually also alreadyequipped with an apparatus for supplying or for removing heat. Duringthe extrusion, the polymer to be processed therefore as a rule need beadditionally exposed only to electromagnetic radiation in order to carryout the method according to the invention. According to the invention,in particular films or fibres can be produced by the extrusion method.

According to the invention, for example, methods in which a polymer meltis produced with the aid of the method according to the invention and isthen further processed in a customary manner, for example to give filmsor fibres, are likewise preferred.

Finally, the method according to the invention can be combined with aninjection moulding method known per se. Here, as in the case of thecombination with a spinning method, the polymer is first melted usingthe method according to the invention and then subjected to a customaryinjection moulding method. In order to prevent the polymer to beprocessed from being converted back into the unfavourable crystallinestructure with formation of the originally present hydrogen bridgebonds, the injection moulding should be effected immediately after thepolymer was melted by the method according to the invention.

According to the invention, an apparatus for carrying out the methodaccording to the invention is also provided. The apparatus according tothe invention which is suitable for carrying out the method according tothe invention has means for holding a polymer, means for exertingpressure on the polymer, means for shearing the polymer, means forsupplying or removing heat and means for irradiating the polymer withelectromagnetic radiation having a wavelength of from 0.8 to 100 μm.

The means which exert pressure on the polymer are preferably also usedfor shearing the polymer. Particularly preferably, these means are tworams whose surfaces are movable relative to one another. An extruderscrew is also preferred.

According to the invention, the means for irradiating the polymer withelectromagnetic radiation are preferably a laser, as already describedabove.

Means for supplying and removing heat are known to a person skilled inthe art. Such means are preferably heating and cooling collars which aremounted in a suitable manner on the apparatus according to theinvention.

With the method according to the invention, it was possible for thefirst time to plastically deform polymers which contain cellulose andchitin. Hydrogen bridge bonds are broken thereby and form again inanother manner after the deformation. The polymer which is deformed bythe method according to the invention and contains cellulose or chitin,preferably in an amount of 10% or more, more preferably 30% or more,more preferably 60% or more, more preferably 75% or more, morepreferably 90% or more, or consists exclusively of cellulose or chitin,therefore differs in its physical structure from the polymers which wereused for the method. Although it is possible to process cellulose andchitin from a solution, reformation of the hydrogen bridge bondslikewise taking place, the structure of the polymers obtained fromsolution differs from the structure of the polymers deformed by themethod according to the invention. Moreover, polymers which areprocessed from a solution inevitably acquire incorporated traces ofsolvents which are not present in the polymers deformed by the methodaccording to the invention. The cellulose thermoplastically deformed bythe method according to the invention and the chitin thermoplasticallydeformed by the method according to the invention, as defined above, aretherefore novel compared with the known forms of cellulose and ofchitin.

The invention is explained in more detail by the following example, withreference to FIG. 1. The example is not limiting.

In FIG. 1,

Reference numeral 1 designates a ram which can rotate about itslongitudinal axis 2

Reference numeral 2 designates the longitudinal axis of the rams 1 and 4

Reference numeral 3 designates a CO₂ laser which can emitelectromagnetic radiation having a wavelength of 10.6 μm

Reference numeral 4 designates a stationary ram having the longitudinalaxis 2

Reference numeral 5 designates the polymer to be deformed

EXAMPLE

Commercially available cotton wool fibres which comprise more than 90%of cellulose and more than 5% of hemicellulose (Ullmann's Encyclopediaof Industrial Chemistry, 5th Edition, 1986, 391) are compressed in acustomary press to give cylinders having a diameter of 3 mm and a heightof 2 mm. The fibre structure is retained. The pressure is 1178 N and theduration of pressing is 3 seconds. The polymer sample 5 substantiallycomprising cellulose forms thereby.

The polymer sample 5 is placed between two cylindrical rams 1 and 4which lie on a common geometrical axis 2 of symmetry. The rams have adiameter of 3 mm and are pressed together with a force of 1178 N. Theythus exert a pressure of 167 N/mm² on the polymer sample 5.

For carrying out the method, the ram 1 is first caused to rotate aboutits own longitudinal axis 2, in particular at a rotational speed of onerevolution per second. The polymer sample is then exposed toelectromagnetic radiation by means of the laser 3. The laser 3 is a CO₂laser having a wavelength of 10.6 μm and a beam power of 280 W. Thelaser beam has an effective diameter of 5 mm at the processing site.This results in a beam intensity of 1.4×10³ W/cm². The beam is pulsedwith a pulse rate of 10 kHZ. The radiation lasts for 7 seconds. Therotation of the ram 1 in relation to the ram 4 and the pressure aremaintained during this radiation time. Under the action of the laserbeam, cotton wool fibres which project laterally between the rams burn.

During the entire method, the apparatus was cooled and was kept at aconstant temperature of 100° C.

After the radiation and the rotation are switched off, the rams 1, 4 aremoved apart. A thin, transparent disc of cohesive film-like material ispresent between the rams 1, 4. The film was clear and had nodiscoloration. The original fibre structure was converted into acohesive continuum. No chemical modification of the cellulose tookplace.

1. A method for the plastic deformation of polymers, comprising treatingpolymers with electromagnetic radiation having a wavelength in the rangefrom 0.8 to 100 μm, and simultaneously treating the polymers withpressure and shearing and thermal energy.
 2. The method according toclaim 1, wherein the heat is supplied to the polymer or heat is removedfrom the polymer during the method.
 3. The method according to claim 1,wherein the electromagnetic radiation is laser radiation.
 4. The methodaccording to any of claim 3, wherein the electromagnetic radiation has awavelength in the range from 1 to 50 μm.
 5. The method according toclaim 1, wherein the pressure acting on the polymer is in a range from 1N/mm² to 5000 N/mm².
 6. The method according to claim 1, wherein theshearing is applied with a force or a torque such that a shear rate inthe range from 10° to 10⁶ s⁻¹ acts on the polymer.
 7. The methodaccording to claim 1, wherein the polymer comprises a polymer which canform intermolecular hydrogen bridge bonds.
 8. The method according toclaim 7, wherein the polymer which can form intermolecular hydrogenbridge bonds is a polysaccharide or polyvinyl alcohol.
 9. The methodaccording to claim 8, wherein the polymer which can form intermolecularhydrogen bridge bonds is selected from the group consisting ofcellulose, chitin, polyvinyl alcohol, a constitutional isomer ofcellulose, a constitutional isomer of chitin and a blend of one or moreof the above polymers.
 10. The method according to claim 9, wherein thepolymer which can form intermolecular hydrogen bridge bonds iscellulose.
 11. The method according to claim 1, wherein the polymer ismelted by means of electromagnetic radiation having a wavelength in therange from 0.8 to 100 μm under the simultaneous action of pressure andshearing and thermal energy and is then extruded, spun to give fibres orprocessed by injection moulding to give a moulding.
 12. An apparatuscomprising a means for holding a polymer, a means for exerting pressureon the polymer, a means for shearing the polymer, a means for supplyingor removing heat and a means for irradiating the polymer withelectromagnetic radiation having a wavelength of from 0.8 to 100 μm. 13.An apparatus according to claim 12, wherein the means for irradiatingthe polymer with electromagnetic radiation having a wavelength of from0.8 to 100 μm is a laser.
 14. An apparatus according to claim 12,wherein the means for shearing the polymer comprises two ram surfacesmovable relative to one another.
 15. An apparatus according to claim 12,wherein the means for exerting pressure on the polymer are alsosimultaneously the means by which the polymer is sheared.
 16. A polymercomprising cellulose or chitin, obtainable by the method according toclaim
 1. 17. The polymer according to claim 16, which is a film, fibreor moulding.